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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

One reliable acute/chronic toxicity data point (Klimisch 1, GLP) for an algal species  -the green algae Pseudokirchneriella subcapitata - has been identified. Based on measured Sr-level in the water column, a 72h-ErC50 and 72h-NOEC of  is reported by Tobor-Kaplon (2010), using  Sr(NO3)2 as test substance.

Key value for chemical safety assessment

EC50/LC50 for freshwater algae:
90.8 mg/L
EC10, LC10 or NOEC for freshwater algae:
90.8 mg/L

Additional information

Read-across statement:

In the aqueous and terrestrial environment, strontium sulfate dissolves in (pore) water releasing strontium cations and sulfate anions.

Sulfate:Sulfates are of low environmental toxicity (OECD SIDS for Na2SO4) as sulfate is essential to all living organisms and their intracellular and extracellular concentrations are actively regulated.

Strontium: No or few ecotoxicological data are available for strontium sulfate itself. For the assessment of the environmental fate and behaviour of strontium substances, a read-across approach is applied based on all information available for inorganic strontium compounds. This is based on the common assumption that after emission of metal compounds into the environment, the moiety of toxicological concern is the potentially bioavailable metal ion (i.e., Sr2+).This assumption is considered valid as the ecotoxicity is only affected by the strontium-ion and not by the counter (sulfate) ion.The speciation and chemistry of strontium is rather simple.

 

As reactive electropositive metal, strontium is easily oxidized to the stable and colourless Sr2+ion in most of its compounds, the chemical behaviour resembling that of calcium and/or barium (Wennig and Kirsch, 1988). In the environment, the element only occurs in one valence state (Sr2+), does not form strong organic or inorganic complexes and is commonly present in solution as Sr2+(Lollar, 2005). Consequently, the transport, fate, and toxicity of strontium in the environment are largely controlled by solubility of different Sr-salts (e. g., SrCO3, Sr(NO3)2, SrSO4, …).

These findings are sufficient justification for the implementation of a read-across strategy with ecotoxicity results obtained in tests that were conducted with different strontium compounds that generate free Sr2+-ions in solution, and this for all relevant environmental endpoints that were considered.

In sum, the environmental hazard assessment is based on strontium.

References:Wennig, R.; Kirsch, N. (1988): Chapter 57 Strontium, In: Seiler, U. G. et al.(eds), Handb. Tox. Inorg. Comp. NY, 631-638

Summary: One reliable acute/chronic toxicity data point (Klimisch 1, GLP) for an algae species - the freshwater green alga Pseudokirchneriella subcapitata - has been identified. No effect (growth rate) was noted at the highest (nominal) test concentration of 100 mg test material/L. Based on measured Sr-levels, this effects levels translates to 43.3 mg Sr/L or 90.8 mg strontium sulfate/L.

Therefore, based on measured Sr-levels in solution, the ErC50 and NOEC are >90.8 and >=90.8 mg SrSO4/L, respectively.